High Energy Physics - Experimental

The Stony Brook High Energy Group focusses on the study of fundamental particles and forces as revealed in the collisions of hadrons at the largest available energies. The mainstay of the current program is at the 2 TeV antiproton-proton collider at Fermilab using the D0 detector. A portion of the research is now based on the deep underground experiment SuperKamiokande, located in Japan. In addition, we have begun a collaboration with the CMS experiment at the Large Hadron Collider at CERN and are developing a program of high energy physics at the Relativistic Heavy Ion Collider (RHIC) under construction at nearby Brookhaven National Laboratory (BNL).

The D0 experiment

Display of a top quark candidate event with an electron (the large magenta arrow), a muon (green tube), two jets of many particles (gray and pink arrows), and the missing transverse momentum carried by neutrinos (large light arrow). The arrow widths are proportional to the energy carried by the object. The lattice work shows the cells of the calorimeter showing significant energy deposit. The spheres represent the amount of energy deposited in the calorimeter cells (orange and white for the electromagnet deposits and blue for hadronic deposits). The faint shadings represent the edges of the sub-detectors.

The Stony Brook-led D0 experiment started its data taking at the Tevatron Collider in mid 1992. The detector is the most advanced instrument available for the study of hadron collisions at very high energies and large transverse momenta. It gives particular stress to the detection of quark and gluon jets, leptons (electrons and muons), and missing transverse momentum which signals the presence of neutrinos of other non-interacting particles. Together, these elements give powerful signatures for detecting new massive particles or rare phenomena with little associated background. Among the physics topics now under investigation by Stony Brook students and faculty are:

• The discovery of the top quark and the study of its properties. The top quark is expected to be the last fundamental fermion in nature and its extremely large mass suggests that it may play a crucial role in the symmetry breaking mechanism of the electroweak interaction. Precision determination of its mass permits sensitive tests of the Standard Model; the study of its production and decay offers many interesting ways to search for new phenomena.
• Studies of the W and Z gauge bosons allow various tests of the electroweak theory. We are engaged in a precision measurement of the W mass; searches for anamolous couplings of gauge bosons; and studies of the W -> tau nu decays.
• Studies of the strong force (Quantum Chromodynamics) and the properties of the elementary quark and gluon constituents within hadrons can be made with a variety of probes. We are examining the production of parton jets, direct photons and photon pairs, W and Z gauge bosons in association with jets, and production of the b-quark to make detailed comparisons with models of the strong force and to deduce the partonic constituents of the hadrons.
• The high energy available in antiproton-proton collisions allows a large range of searches for new phenomena. We are involved in searches for supersymmetric particles (a new particle paired with each known particle but with opposite fermion/boson composition). If supersymmetric particles exist, they point the way for new unifications of the fundamental forces. Other searches are aimed at excited quarks or gauge bosons, or families of particles with a new class of `flavor'.

We working on modifications of the D0 detector which will accompany a large increase in accelerator luminosity late in this decade. These upgrades will open additional physics opportunities to study heavy flavor quarks. Stony Brook staff are participating in several aspects of this work; new calorimeter electronics; development of preshower detectors for electron and photon identification at trigger and offline levels; and development of new reconstruction software.

Super Kamiokonde

A view of the SuperKamiokonde detector during its construction.

The SuperK group at Stony Brook

Professor Chang-Kee Jung's group participates in the Super Kamiokonde project which will study the interactions of neutrinos in the low-background environment of a a former gold mine deep underground in Japan. Physics topics include measurement of solar neutrino fluxes, testing of the standard astrophysical models and sensitive to possible neutrino oscillations. In addition, the experiment will study anamolies in terrestrially produced neutrinos and will pursue the search for proton decay.

Atlas

For more information:

• High Energy Group WWW page
• Publications
• Faculty
• Staff
• Postdocs
• Students

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